Gaseous electric discharge device



Dec. 21, 1937.

N. w. H. A DDlNK GASEOUS ELECTRI DISCHARGE DEVICE Filed Aug. 2:5, 195'! lNvENToR NicoIaas W. HAddink ORNEY Patented Dec. 21, 1937 UNITED STATES GASEOUS ELECTRIC DISCHARGE if Nicolaas W. H. Addink, Eindhoven, Netherlands,

assignor 'to General Electric Company, a corporation of New York Application August 23, 1937, Serial No. 160,549

In Germany September 3, 1936 1 'Claim.

The present invention relates to gaseous elec-- tric discharge devices generally and. more particularly the invention relates to such devices having a luminescent material associated therewith to supplement and complement the light emitted by the discharge in the device.

A large variety of luminescent materials, that is, fluorescent or phosphorescent materials, are useful in transforming the rays of shorter wave 'length, such as ultra violet rays, emitted by the discharge into rays of longer wave length within the visible range. Such materials include tun states, such as calcium tungstate; sulphides, such as zinc sulphide or calcium sulphide, and oxides, such as zinc oxide. These materials are mounted in light receiving relation to the lamp device as by being applied to the container of the lamp device, a bulb enclosing the lamp device or on a reflector for the lamp device, the location thereof being determined by the characteristics of the particular type of material used and by other factors. I have observed that the light output of the luminescent sulphides diminishes and the color of the light emitted thereby changes after a comparatively short period of irradiation. This is particularly noticeable when the density of the light incident at the surface of the luminescent, sulphide is high as is the case when such materials are irradiated by the light from a high pressure mercury vapor discharge lamp.

The object of the present invention is to provide a lamp, unit comprising a luminescent sulphide and a gaseous electric discharge lamp device in which the sulphide retains its original spectral emission and a high light output substantially unchanged for a long useful life. Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description.

I have discovered that the loss in the light output and the change in the color of the light emitted by luminescent sulphides during irradiation by the light from a gaseous electric discharge device is caused by the presence of halides, such as sodium chloride and potassium chloride, in the luminescent sulphide. These deleterious materials are present in the commercially obtainable luminescent sulphides in extensive use in the art. Having discovered the cause of the dimculty the solution of the problem is comparatively simple. Since these deleterious materials are soluble in water they can be removed by washing the luminescent sulphides. When no halide is detectable in the water the luminescent (Cl. FIG- 122) sulphide is considered tobe halide free and, as

I have demonstrated, has a long useful life when used in conjunction with gaseous electric dissoftening temperature, such as quartz, and has therein a quantity of mercury, the vapor of which is luminosity producing during the operation of the device, and a starting gas, such as argon. The discharge device is capable of operation with a mercury vapor pressure of 20 atmospheres or 20 higher and is a highly eflicient, concentrated. light source. Electric discharge devices of this type are described in the co-pending application, Serial Number 46,952 filed October 26, 1935, and reference is had to said copending application 5 for the structural details and operating characteristics of discharge lamps of this type.

The gaseous electric discharge lamp device is mounted in a sealed bulb 2v consisting of one of the usual container glasses, such as a lead or a 30 lime glass. Said bulb 2 has a stem 3 into the .press of which the current leads 4 and 5 for the discharge lamp device are fused. Said discharge lamp device is supported in said bulb 2 by said leads 4 and 5. The inner surface of the 35 spherical part of the bulb 2 has a coating 6 thereon consisting of a luminescent sulphide, such as zinc sulphide or cadmium sulphide, which has been washed in distilled water until no halides are detectable in the water. is, applied to said bulb 2 by methods now known in the art, such as by using a binding agent of phosphoric acid dissolved in methyl alcohol. The bu1b.2 is either evacuated or filled with an inert gas, such as nitrogen, after the coating 6 is ap- 45 plied thereto and the discharge lamp device is mounted therein and serves as a heat conservator for the discharge lamp device.

The coating 6 4o pointed out in the annexed claim certain novel features of the invention, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its use and operation may be made by those skilled in the art without departing from the broad spirit and. scope of the invention, for example, other types of discharge lamps which emit rays capable of exciting the lumines- 10 cent sulphides are used, when desired.

What I claim as new and desire to secure by Letters Patent of the United States, is:-

A lamp unit comprising in combination a gaseous electric discharge lamp device and a luminescent sulphide mounted in light receiving relation to said lamp device, said material being emissive in the visible spectral ranges when irradiated by said lamp and containing halides in such small amounts that the light output and the color of the light emitted by said sulphide is substantially unaffected by said halides for a long useful operating life of the lamp unit.

NICOLAAS W. H. ADDINK. 

